Device to block weft yarn during cutting on a weft feeder

ABSTRACT

Device to block weft yarn associated with a measuring weft feeder for fluid jet looms. The device is located downstream of the outlet yarn guide and/or of the antiballoon device of the feeder, and comprises a single elongated body which includes: an inlet cone and a cylindrical channel crossed by the weft yarn, the common axis of which is the longitudinal axis of the device; a core to block the yarn, movable into a guide perpendicularly to the axis and adapted to penetrate into the channel through an opening thereof; electromagnetic elements acting on the core against a return spring; and a bush associated to the channel, in correspondence of the opening, to form a contrast surface onto which the core engages in order to block the yarn.

FIELD OF THE INVENTION

The present invention concerns improvements in measuring weft feedersfor fluid jet looms, namely those special weft yarn feeders from whichthe yarn is drawn by the main nozzle of the loom and the yarn turnsbeing unwound from the weft feeder drum are counted through anappropriate system.

BACKGROUND OF THE INVENTION

As is known, in such feeders, the weft yarn inserted in the loom shed isstopped, after having reached the preset length, by a controlled deviceusually comprising a movable rod which engages the edge of the drum bypenetrating with slack into a hole formed on said drum, the weft yarnstopping against said rod and being braked thereby.

The present invention proposes to solve the problems arising just afterthe weft yarn has been stopped and, in particular, to provide for anefficient blocking of said yarn just after it has been cut by theappropriate cutting devices of the loom.

It should be remembered that, for the loom cutting devices to correctlyperform their function, it is necessary for the weft yarn lengthextending between the measuring weft feeder and the fabric being wovento be sufficiently tensioned at the moment in which it is being cut;consequently, since just after cutting there is a sudden decrease inweft yarn tension, this causes oscillations on the yarn starting fromits cut end and travelling backwards to the point in which the yarn isblocked by the rod of the stopping device on the weft feeder drum. Theseoscillations may even continue up to involving the yarn turns wound onsaid drum.

These oscillations, turning on the yarn into strong transversal andlongitudinal waves, may cause various inconveniences, such as:

a) Wedging-in of the weft yarn beneath the rod of the stopping device,when this latter is already acting into the drum hole.

b) Ruffling of the yarn turns wound on the drum, with possibleoverlapping thereof, whereby, during the next weft yarn insertion, theturns will no longer unwind regularly one at a time from the drum, butmay be drawn by two or more turns at a time getting entangled at theoutlet of the drum.

It is evident that, both in the first case and in the second case,measuring errors might occur, which may in turn cause stopping of theloom, thereby reducing the efficiency of the machine, or else give riseto faults, which are not detected by the loom control devices and willthus deteriorate the quality of the fabric being produced.

To try and overcome the problem mentioned in a), the applicant hasalready developed in the last years different improvements in theelectromagnetic weft yarn stopping units adopted on measuring weftfeeders for fluid jet looms: the most interesting solutions are thosedescribed and claimed in IT-U-209674, and in the recent EP-363938.

An attempt to solve the problem mentioned in b) had instead been made,always by the applicant, by adopting an additional device mounted incorrespondence of the yarn guide eyelet at the outlet of the measuringweft feeder: this solution is described in EP-239055. Nevertheless, saiddevice was not able to fully solve the problem in that, since the weftyarn was not blocked but merely deviated, it was still likely to loosenaround the drum.

SUMMARY OF THE INVENTION

The present invention now proposes instead to thoroughly solve theproblem by means of a totally new device, which is able to firmly blockthe weft yarn at the outlet of the weft feeder while its cutting takesplace in the loom.

This device, which is to be associated to measuring weft feeders forfluid jet looms, just downstream of the outlet yarn guide and/or of theantiballoon device of said feeders, is characterized in that itcomprises a single elongated body including: an inlet cone and acylindrical channel, crossed by the weft yarn, the common axis of whichis the longitudinal axis of said device; a core to block the weft yarn,movable into a guide perpendicularly to said axis and adapted topenetrate into said channel through an opening thereof; electromagneticmeans acting on said core against a return spring; and a bush associatedto said channel, in correspondence of said opening, to form a contrastsurface onto which said core engages in order to block the weft yarn.

In said device, the core is suitably cylindrical and its diameter iswider than that of the channel crossed by the weft yarn, while thecontrast surface of the bush comprises a bottom layer of dampingmaterial and a covering of shockproof and wear resistant material.

Preferably, the spring return means, which consist of a cylindricalhelical spring, tend to keep the core in tight engagement with saidcontrast surface inside the channel, so as to block the weft yarn, whilesaid electromagnetic means, which consisting of a coil surrounding saidcore, when energized, lead said core out of the channel, causing it todisengage from said surface and to release the weft yarn, leaving itfree to cross the channel of the device.

In an active condition of the device, said electromagnetic means arede-energized slightly later than the issue of the last signal of weftyarn unwinding from the drum of the measuring weft feeder, so that,during weft yarn cutting in the loom, said yarn is blocked by thedevice, while the engagement of the core with the contrast surface ofthe channel still remains.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the device according to thepresent invention will anyhow be more evident from the followingdetailed description of a preferred embodiment thereof, given by way ofexample and illustrated on the accompanying drawings, in which:

FIG. 1 is an axial section view of the device, showing the weft yarnblocking core and the spring means associated thereto in an inactivecondition; and

FIG. 2 is an axial section view of the device, showing the weft yarnblocking core and the spring means associated thereto in an activecondition.

DETAILED DESCRIPTION OF THE INVENTION

As shown on the drawings, the device to block the weft yarn of thepresent invention essentially consists of a single elongated body 1 withlongitudinal axis 2, comprising an inlet cone 3 and a cylindricalchannel 4 meant to be crossed by the weft yarn F, the cone 3 and thechannel 4 being aligned with their axes coinciding with the axis 2 ofthe body 1. The device is meant to be associated to measuring weftfeeders for fluid jet looms, to which it is applied by way of the cone 3just downstream of the outlet yarn guide and/or of the antiballoondevice of said feeders.

The body 1 of the device according to the invention comprises moreover acylindrical core 5 to block the weft yarn F, movable into a guide 6perpendicularly to the axis 2 and adapted to penetrate into the channel4 through a transversal opening 7 thereof. Electromagnetic means in theform of a coil 8 surround the core 5, onto which there also acts acylindrical helical spring 9. A bush 11 is associated to the channel 4in correspondence of the opening 7, so as to form a contrast surface 10onto which the core 5 engages in order to block the weft yarn F. Thecontrast surface 10 comprises a bottom layer of damping material and acovering of shockproof and wear resistant material.

The device according to the invention is normally inactive (FIG. 1) toallow the weft yarn F to freely cross the channel 4. To keep said devicein an inactive condition, it is necessary to energize the coil 8 which,overcoming the action of the return spring 9, causes the core 5 to movebackward (as shown in FIG. 1) disengaging from the surface 10, and leadssaid core out of the channel 4. When the coil 8 is de-energized, thedevice becomes active (FIG. 2), in that the spring 9 pushes the core 5into the opening 7 of the channel 4 (as shown in FIG. 2) and presses itagainst the contrast surface 10 of the bush 11, so as to block the weftyarn F, crossing said channel, between the core 5 and the surface 10.

The device according to the invention is inactive (FIG. 1) when the weftyarn F is being inserted into the loom; during this step, the yarn isfree to slide through the channel 4, the core 5 being kept out of theopening 7 by the coil 8, suitably energized, which attracts it againstthe action of the return spring 9.

The device becomes active (FIG. 2) at the end of the weft yarn insertionstep, by de-energizing the coil 8: the spring 9 thus moves the core 5back into the opening 7 of the channel 4 so as to block the weft yarn Fagainst the surface 10 of the bush 11. In this condition, the yarn canno longer slide through the channel 4, nor loosen around the drum of themeasuring weft feeder.

The de-energizing of the coil 8, to turn the device active, is carriedout somewhat later than the issue of the last signal indicating that theweft yarn turns have unwound from the drum of the measuring weft feeder,namely when the weft yarn has positively stopped (at the end ofinsertion in the loom), and before it is cut by the appropriate meansprovided in the loom. It is actually in this step that the weft yarn iskept firmly gripped between the core 5 and the contrast surface 10, andit remains in this condition during cutting and up to start of thefollowing insertion.

The object of the invention is thereby reached. It is in fact just afterthe cutting step that the oscillations on the weft yarn may be produced,involving the previously described inconveniences. The device of theinvention thus proves to be extremely helpful to eliminate suchdrawbacks, as it prevents undesired waves travelling backwards from theloom cutting devices through the launching nozzle from extending up tothe weft yarn length between the yarn guide at the outlet of themeasuring weft feeder (and now the device of the invention) and the yarnreserve drum, thereby ruffling the yarn turns wound thereon.

The core 9 is then returned to its inactive position by energizing thecoil 8 and thus freeing again the channel 4 at the start of the nextweft yarn insertion.

The device according to the invention is normally associated to ameasuring weft feeder, so as to form an integrating part thereof, by wayof its inlet cone 3 acting as an efficient element of connection withthe antiballoon device usually provided at the outlet of said feeders.As an alternative, said device can be simply mounted downstream of theoutlet yarn guide of the measuring weft feeder.

The device of the present invention is full of advantageous properties,which contribute to the efficient operation of the weft feeders to whichsaid device is associated and of the looms adopting such feeders. Infact:

1) The device of the invention is adapted to complete a nozzle for theautomatic insertion of the weft yarn, whereby, connected to otherdevices commonly used on measuring weft feeders for fluid jet looms, itallows to obtain the full insertion of the weft yarn from the inlet tothe outlet of the feeder.

2) The device of the invention can be mounted on automatic systemsprovided to mend the weft yarn, wherein it may be required to launch theyarn through the weft feeder up to the loom nozzle.

3) The device of the invention can be easily connected at the outlet ofa funnel-shaped antiballoon device.

4) Unlike the known plate brakes used in some types of looms, whichalways have a very limited stroke (reduced space between the two plateswhen the brake is open), the device of the invention, when inactive,leaves the channel crossed by the yarn totally free, and thus by nomeans hinders the sliding of the yarn during its insertion.

5) Since the channel is totally closed by the blocking core, when thislatter is caused to act, and since the diameter of said core is widerthan that of the channel, the inconvenience of the known plate brakes,caused by the weft yarn emerging from the plate, no longer arises withthe device of the invention. In fact, with the known plate brakes, onewas forced to use an inlet yarn guide eyelet, as well as an outlet oneof small diameter, in order to keep the yarn guided under the plate,with evident limitations as far as the size of the yarn being used forweaving and the practicality of the manual yarn inserting operation.

6) The cleaning of the device of the invention is obtained thanks to thecontinuous passage of weft yarn, which constantly laps on the channelwalls and simultaneously produces an air flow allowing to prevent thepiling up of dust.

7) Downstream of the device of the invention, it is possible toassociate a controlled weft recovery device at the outlet of themeasuring weft feeder.

8) The device of the invention facilitates the operation of manualreinstatement of the weft yarn reserve, preventing when the yarn windingmember starts to operate, said yarn from being pulled backward towardsthe weft feeder drum, thereby slipping out of the operator's hand andthus requiring to be inserted again into the antiballoon device, or intothe yarn guide eyelet at the outlet of the feeder.

9) The device of the invention is controlled directly by the weft feederand thus operates in full synchronism with the actual position of theweft yarn, with no need to use any further mechanical elements connectedto the loom, or any sensors or signals to establish said synchronism.

It is understood that there may be other practical embodiments of thedevice according to the present invention, differing form the onedescribed heretofore, but still falling within its scope. In particular,the action of the device and of the core to block the weft yarn can beobtained through electromagnetic means, instead of spring means, whilespring means could be used to stop the action of said device; likewise,use could be made of electromagnetic means, either on their own, orcombined with spring means, both to make the device active and to keepit inactive.

I claim:
 1. Device for blocking weft yarn associated with a measuringweft feeder for fluid jet looms, said device adapted to be located justdownstream of at least one of an outlet yarn guide and an antiballoondevice of said feeder, the device comprising: a single elongated bodywhich includes: an inlet cone and a cylindrical channel, crossed by theweft yarn, said inlet cone and cylindrical channel having an axis whichis common to the longitudinal axis of said device; a core for blockingthe yarn, said core being movable into a guide perpendicularly to saidaxis and adapted to penetrate into said channel through an openingthereof; an electromagnetic means acting on said core against springreturn means; and said channel having, in correspondence of saidopening, a bush which forms a contrast surface onto which said coreengages in order to block the yarn.
 2. Device according to claim 1,wherein said core is cylindrical and has a diameter which is wider thanthat of the channel crossed by the yarn.
 3. Device according to claim 1,wherein said contrast surface of the bush comprises a bottom layer ofdamping material, and a covering of shockproof and wear resistantmaterial.
 4. Device according to claim 1, wherein said spring returnmeans urges the core in engagement with said contrast surface inside thechannel, blocking the yarn, while said electromagnetic means, whenenergized, lead said core out of the channel, causing it to disengagefrom said surface and to release the yarn.
 5. Device according to claim1, wherein said spring return means consists of a cylindrical helicalspring.
 6. Device according to claim 1, wherein said electromagneticmeans consist of a coil surrounding said core.
 7. Device according toclaim 1, including means for de-energizing said electromagnetic meansjust after an indication of weft yarn unwinding from a drum of themeasuring weft feeder, so that during weft yarn cutting in the loom,said yarn is blocked by the device.